68000 NV

At this point this is minimal information about 68000 pcb design ..main features:

Schematic Diagram

Prototype pcb made ..Top View

When Running with all chips on pcb current consumption about 450mA at 5V.

This is the original prototype where 2 nvRAM chips are used for even/ odd Ram

The pld  file is as follows for the pcb version ..

PLD file

Name            68K ram/rom;

Partno          0001;

Revision        pcbversion_rom_nvRAM_version;

Date            6/8/18;

Designer        mc;

Company         mcoz;

Location        oz;

Assembly        manual;

Device          g22v10;

/** Inputs **/

pin [2..6] = [a19..a23] ;

pin 7 = rnw;

pin 8 = nlds;

pin 9 = nuds;

pin 10 = nas;

pin 11 = sio_ndtack;

/** Outputs **/

pin 23 = !cs_sio;

pin 22 = !cs_ram;

pin 21 = !lwr;

pin 20 = !lrd;

pin 19 = !uwr;

pin 18 = !urd;

pin 17 = !dtack;

pin 16 = rom_nvRAM;

/** Declarations and Intermediate Variable Definitions **/

field ioaddr= [a19..23];

rom_nvRAM_eqn = (ioaddr:[F0XXXX..FFXXXX]);

cs_ram_eqn   = (ioaddr:[00XXXX..7FXXXX] # ioaddr:[F0XXXX..FFXXXX])& !nas ;

cs_sio_eqn   = (ioaddr:[E8XXXX..EFXXXX])&!nas & !nlds ;

/** Logic Equations **/

cs_ram = cs_ram_eqn;

cs_sio = cs_sio_eqn;

dtack =!nas;

lwr = !rnw & !nlds;

lrd = rnw & !nlds;

uwr = !rnw & !nuds;

urd = rnw & !nuds;

rom_nvRAM = rom_nvRAM_eqn;

Image files of 2 memory chips:

Following is a screen capture of the monitor booting up and  display command initiated ..

Note: Try not to use bottom area of the RAM area as it contains the RESET vectors ... if they get overwritten then you need to reprogram the nvRAM chips again with fresh copy of bin files below...

Here is completed PCB using the 68k chip...

 There is few mods to make the PCB operate ...

See pics below..

The information about Monitor etc ...see following web pages for more info .. Tiny Giant 68000 SBC